{"title":"科恩扩展中的滤门格尔实数集","authors":"Hang Zhang, Shuguo Zhang","doi":"10.1002/malq.202300008","DOIUrl":null,"url":null,"abstract":"<p>We prove that for every ultrafilter <span></span><math>\n <semantics>\n <mi>U</mi>\n <annotation>$\\mathcal {U}$</annotation>\n </semantics></math> on <span></span><math>\n <semantics>\n <mi>ω</mi>\n <annotation>$\\omega$</annotation>\n </semantics></math> there exists a filter <span></span><math>\n <semantics>\n <mi>F</mi>\n <annotation>$\\mathcal {F}$</annotation>\n </semantics></math> on <span></span><math>\n <semantics>\n <msup>\n <mn>2</mn>\n <mrow>\n <mo><</mo>\n <mi>ω</mi>\n </mrow>\n </msup>\n <annotation>$2^{&lt;\\omega }$</annotation>\n </semantics></math> which is <span></span><math>\n <semantics>\n <mi>U</mi>\n <annotation>$\\mathcal {U}$</annotation>\n </semantics></math>-Menger and <span></span><math>\n <semantics>\n <mrow>\n <mi>χ</mi>\n <mo>(</mo>\n <mi>F</mi>\n <mo>)</mo>\n <mo>=</mo>\n <mi>b</mi>\n <mo>(</mo>\n <mi>U</mi>\n <mo>)</mo>\n </mrow>\n <annotation>$\\chi (\\mathcal {F})=\\mathfrak {b}(\\mathcal {U})$</annotation>\n </semantics></math>. We show that in the Cohen model there exists such <span></span><math>\n <semantics>\n <mi>F</mi>\n <annotation>$\\mathcal {F}$</annotation>\n </semantics></math> which are tall by using a construction of Nyikos's [10]. These answer a question of Das [2, Problem 7]. We prove that there is a Menger filter of character <span></span><math>\n <semantics>\n <mi>d</mi>\n <annotation>$\\mathfrak {d}$</annotation>\n </semantics></math> that is not Hurewicz in the <span></span><math>\n <semantics>\n <mi>κ</mi>\n <annotation>$\\kappa$</annotation>\n </semantics></math>-Cohen model where <span></span><math>\n <semantics>\n <mrow>\n <mi>κ</mi>\n <mo>></mo>\n <msub>\n <mi>ω</mi>\n <mn>1</mn>\n </msub>\n </mrow>\n <annotation>$\\kappa &gt;\\omega _{1}$</annotation>\n </semantics></math> is uncountable regular. This shows that the positive answer to a question of Hernández-Gutiérrez and Szeptycki [3, Question 2.8] is consistent with <span></span><math>\n <semantics>\n <mrow>\n <mi>b</mi>\n <mo><</mo>\n <mi>d</mi>\n </mrow>\n <annotation>$\\mathfrak {b}&lt;\\mathfrak {d}$</annotation>\n </semantics></math>. We also study the filter <span></span><math>\n <semantics>\n <mi>F</mi>\n <annotation>$\\mathcal {F}$</annotation>\n </semantics></math> generated by the set of mutually Cohen reals in the <span></span><math>\n <semantics>\n <mi>κ</mi>\n <annotation>$\\kappa$</annotation>\n </semantics></math>-Cohen model. We prove that <span></span><math>\n <semantics>\n <mrow>\n <mi>b</mi>\n <mrow>\n <mo>(</mo>\n <mi>F</mi>\n <mo>)</mo>\n </mrow>\n <mo>=</mo>\n <msub>\n <mi>ω</mi>\n <mn>1</mn>\n </msub>\n </mrow>\n <annotation>$\\mathfrak {b}(\\mathcal {F})=\\omega _{1}$</annotation>\n </semantics></math> and <span></span><math>\n <semantics>\n <mrow>\n <mi>d</mi>\n <mo>(</mo>\n <mi>F</mi>\n <mo>)</mo>\n <mo>=</mo>\n <mi>κ</mi>\n </mrow>\n <annotation>$\\mathfrak {d}(\\mathcal {F})=\\kappa$</annotation>\n </semantics></math> and every <span></span><math>\n <semantics>\n <msup>\n <mo>≤</mo>\n <mo>∗</mo>\n </msup>\n <annotation>$\\mathord {\\le ^{*}}$</annotation>\n </semantics></math>-dominating family in the ground model is <span></span><math>\n <semantics>\n <mi>F</mi>\n <annotation>$\\mathcal {F}$</annotation>\n </semantics></math>-unbounded in extension. Two questions are posed.</p>","PeriodicalId":49864,"journal":{"name":"Mathematical Logic Quarterly","volume":"70 2","pages":"224-232"},"PeriodicalIF":0.4000,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Filter-Menger set of reals in Cohen extensions\",\"authors\":\"Hang Zhang, Shuguo Zhang\",\"doi\":\"10.1002/malq.202300008\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>We prove that for every ultrafilter <span></span><math>\\n <semantics>\\n <mi>U</mi>\\n <annotation>$\\\\mathcal {U}$</annotation>\\n </semantics></math> on <span></span><math>\\n <semantics>\\n <mi>ω</mi>\\n <annotation>$\\\\omega$</annotation>\\n </semantics></math> there exists a filter <span></span><math>\\n <semantics>\\n <mi>F</mi>\\n <annotation>$\\\\mathcal {F}$</annotation>\\n </semantics></math> on <span></span><math>\\n <semantics>\\n <msup>\\n <mn>2</mn>\\n <mrow>\\n <mo><</mo>\\n <mi>ω</mi>\\n </mrow>\\n </msup>\\n <annotation>$2^{&lt;\\\\omega }$</annotation>\\n </semantics></math> which is <span></span><math>\\n <semantics>\\n <mi>U</mi>\\n <annotation>$\\\\mathcal {U}$</annotation>\\n </semantics></math>-Menger and <span></span><math>\\n <semantics>\\n <mrow>\\n <mi>χ</mi>\\n <mo>(</mo>\\n <mi>F</mi>\\n <mo>)</mo>\\n <mo>=</mo>\\n <mi>b</mi>\\n <mo>(</mo>\\n <mi>U</mi>\\n <mo>)</mo>\\n </mrow>\\n <annotation>$\\\\chi (\\\\mathcal {F})=\\\\mathfrak {b}(\\\\mathcal {U})$</annotation>\\n </semantics></math>. We show that in the Cohen model there exists such <span></span><math>\\n <semantics>\\n <mi>F</mi>\\n <annotation>$\\\\mathcal {F}$</annotation>\\n </semantics></math> which are tall by using a construction of Nyikos's [10]. These answer a question of Das [2, Problem 7]. We prove that there is a Menger filter of character <span></span><math>\\n <semantics>\\n <mi>d</mi>\\n <annotation>$\\\\mathfrak {d}$</annotation>\\n </semantics></math> that is not Hurewicz in the <span></span><math>\\n <semantics>\\n <mi>κ</mi>\\n <annotation>$\\\\kappa$</annotation>\\n </semantics></math>-Cohen model where <span></span><math>\\n <semantics>\\n <mrow>\\n <mi>κ</mi>\\n <mo>></mo>\\n <msub>\\n <mi>ω</mi>\\n <mn>1</mn>\\n </msub>\\n </mrow>\\n <annotation>$\\\\kappa &gt;\\\\omega _{1}$</annotation>\\n </semantics></math> is uncountable regular. This shows that the positive answer to a question of Hernández-Gutiérrez and Szeptycki [3, Question 2.8] is consistent with <span></span><math>\\n <semantics>\\n <mrow>\\n <mi>b</mi>\\n <mo><</mo>\\n <mi>d</mi>\\n </mrow>\\n <annotation>$\\\\mathfrak {b}&lt;\\\\mathfrak {d}$</annotation>\\n </semantics></math>. We also study the filter <span></span><math>\\n <semantics>\\n <mi>F</mi>\\n <annotation>$\\\\mathcal {F}$</annotation>\\n </semantics></math> generated by the set of mutually Cohen reals in the <span></span><math>\\n <semantics>\\n <mi>κ</mi>\\n <annotation>$\\\\kappa$</annotation>\\n </semantics></math>-Cohen model. We prove that <span></span><math>\\n <semantics>\\n <mrow>\\n <mi>b</mi>\\n <mrow>\\n <mo>(</mo>\\n <mi>F</mi>\\n <mo>)</mo>\\n </mrow>\\n <mo>=</mo>\\n <msub>\\n <mi>ω</mi>\\n <mn>1</mn>\\n </msub>\\n </mrow>\\n <annotation>$\\\\mathfrak {b}(\\\\mathcal {F})=\\\\omega _{1}$</annotation>\\n </semantics></math> and <span></span><math>\\n <semantics>\\n <mrow>\\n <mi>d</mi>\\n <mo>(</mo>\\n <mi>F</mi>\\n <mo>)</mo>\\n <mo>=</mo>\\n <mi>κ</mi>\\n </mrow>\\n <annotation>$\\\\mathfrak {d}(\\\\mathcal {F})=\\\\kappa$</annotation>\\n </semantics></math> and every <span></span><math>\\n <semantics>\\n <msup>\\n <mo>≤</mo>\\n <mo>∗</mo>\\n </msup>\\n <annotation>$\\\\mathord {\\\\le ^{*}}$</annotation>\\n </semantics></math>-dominating family in the ground model is <span></span><math>\\n <semantics>\\n <mi>F</mi>\\n <annotation>$\\\\mathcal {F}$</annotation>\\n </semantics></math>-unbounded in extension. Two questions are posed.</p>\",\"PeriodicalId\":49864,\"journal\":{\"name\":\"Mathematical Logic Quarterly\",\"volume\":\"70 2\",\"pages\":\"224-232\"},\"PeriodicalIF\":0.4000,\"publicationDate\":\"2024-07-15\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Mathematical Logic Quarterly\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1002/malq.202300008\",\"RegionNum\":4,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q4\",\"JCRName\":\"LOGIC\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Mathematical Logic Quarterly","FirstCategoryId":"100","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/malq.202300008","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"LOGIC","Score":null,"Total":0}
We prove that for every ultrafilter on there exists a filter on which is -Menger and . We show that in the Cohen model there exists such which are tall by using a construction of Nyikos's [10]. These answer a question of Das [2, Problem 7]. We prove that there is a Menger filter of character that is not Hurewicz in the -Cohen model where is uncountable regular. This shows that the positive answer to a question of Hernández-Gutiérrez and Szeptycki [3, Question 2.8] is consistent with . We also study the filter generated by the set of mutually Cohen reals in the -Cohen model. We prove that and and every -dominating family in the ground model is -unbounded in extension. Two questions are posed.
期刊介绍:
Mathematical Logic Quarterly publishes original contributions on mathematical logic and foundations of mathematics and related areas, such as general logic, model theory, recursion theory, set theory, proof theory and constructive mathematics, algebraic logic, nonstandard models, and logical aspects of theoretical computer science.